The present disclosure describes methods and compositions related to hexahydrotriazine materials for use as barrier coatings in the field of electronics.
Conformal polymer barrier coatings are used to protect electronic articles, such as printed circuit boards and electronic components, from corrosion caused by moisture and other contaminants, including sulfur and its compounds, which can cause short circuits from dendrite growth, electromigration of metal between conductors, and other ill effects. The coatings may also protect from organic solvents, abrasion, vibration, and help maintain the dielectric or insulation resistance of the circuit board. The coatings are applied in thin layers (a few mils or a fraction of a mm) onto electronic articles typically by dipping, spraying or simple flow coating, and increasingly by select coating or robotic dispensing. In some cases, the coating may be vapor deposited from a precursor. Examples of polymeric materials used as conformal coatings are: acrylics, epoxies, urethanes, parylene and polysiloxanes (silicones).
Polysiloxanes are used as conformal coatings for electronic articles because of their thermal resistance, flexibility, vibration damping properties, good adhesion to circuit boards, and water repellency. However, polysiloxanes have limited gas barrier properties, which decreases their ability to protect electronics from corrosive contaminants, such as sulfur and sulfur compounds. This is because of the large free volume inherent in polysiloxanes, which can allow the permeation of gases, such as sulfurous gases, through the material. To overcome this inherent weakness, polysiloxane coatings are applied at thicknesses that are much greater than other conformal coatings, such as about 200 micrometers, which is about 10 times thicker than other conformal coatings. Unfortunately, thick conformal coatings increase material costs and application time, so it would be an advantage to apply a thinner conformal coating that is also an improved barrier to sulfur and sulfur compounds, so as to prevent corrosion and short circuits in sensitive electronic circuits and components.